Because of rapid cooling and particularly non-uniform cooling in the high pressure die casting process, a significant amount of residual stress can be developed in HPDC engine parts. With cast-in-place liners, even more residual stress is produced in the liners and surrounding aluminum.
High stresses in the liners at the interbore areas can cause cracking during post-cast machining and durability testing. Conventional lower temperature ageing heat treatment post HPDC to strengthen the aluminum alloy blocks has proven to produce little effect of relieving the cast residual stress. In some cases, liners made from high strength/high durability materials are used to avoid the cracking and fracturing that frequently occurs during machining or testing as a result of residual stresses in the parts after the HPDC process.
It is appreciated that the use of high strength/high durability materials is effective in mitigating the issues resulting from residual stresses affecting cast-in-place liners after the HPDC engine process, this approach is known to be costly, harder to machine, and can reduce fuel efficiency due to increased material weight. As such, aspects of the following exemplary method provides an alternative approach that addresses the issues associated with post-HPDC residual stresses while avoiding the concerns that arise with using high strength/high durability material liners.